Mobile power units are self-contained power modules that can be permanently or temporarily connected to an offboard facility, for example to a home, a hospital, or a factory, to provide primary, supplemental, and emergency backup power. Cables extend from a distribution grid of the facility to the mobile power units and are selectively connected to the mobile power units by way of load interruption devices, for example generator breakers. Additional load breakers are commonly associated with different components and/or branches of the facility's distribution grid.
During operation of the mobile power units, fault conditions can occur that should be isolated to minimize damage to the facility and to the mobile power units. These fault conditions can include over-current conditions and over- or under-voltage conditions caused by open-circuits and short-circuits. Whenever an over-current fault condition is detected, all breakers, including the generator breaker and the load breakers, trip to disconnect the mobile power units from the branches and components of the facility, thereby isolating the open- or short-circuits.
Although existing power distribution systems described above may adequately isolate fault conditions in some situations, they can cause inefficiencies, production losses, and increased operating costs. In particular, even if the fault condition is associated with only one component or one distribution branch of a facility, existing distribution systems disconnect power from all components and branches of the facility and maintain the disconnections until the fault condition is corrected. In these situations, critical components and/or branches not directly associated with the fault condition are unnecessarily shut down, thereby reducing efficiency and productivity of the facility. In addition, each breaker must be individually reset, which can require significant time and labor, thereby increasing operating costs of the facility.
One attempt to reduce operational interruptions caused by fault conditions at a facility is described in U.S. Patent Publication No. 2010/0039741 (the '741 publication) of Booth et al. published on Feb. 18, 2010. In particular, the '741 publication discloses an electrical protection arrangement for a distribution network that is provided between a power source and multiple electric loads. The arrangement comprises multiple fault current flow detectors set in a hierarchy of levels, and a controller configured to actively trip a circuit breaker associated with each fault current flow detector. The controller determines, by sequential movement along a fault path, at which level in the hierarchy of levels the circuit breaker should be tripped to isolate parts of the electrical distribution network. Generally, the lowest level within the hierarchy of levels is tripped first to isolate a minimum amount of the electrical distribution network, leaving the remainder of the network operational.
Although perhaps helpful in reducing operational interruptions in some situations, the electrical protection arrangement of the '741 publication may still be problematic. In particular, the arrangement of the '741 publication may require specialized and dedicated detectors and controllers that increase a cost of the arrangement. In addition, the arrangement of the '741 publication may not be applicable and/or provide little benefit to networks that include mobile power units.
The disclosed power distribution system is directed to overcoming one or more of the problems set forth above and/or other problems of the prior art.